Describe the axillary approach to blocking the brachial plexus.
There are four different methods for
ascertaining the correct position of the needle: paresthesia, transarterial,
nerve stimulator, or blunt needle through the sheath method. This block
requires the patient to lie supine with the arm abducted to a 90° angle.
The transarterial method is the method most
com-monly used. With this method, the axillary artery is palpated in the axilla
and stabilized between two fingers. A 23G 11/2-inch blunt-tipped
needle is advanced toward the pulsations. A pop is usually appreciated as the
needle enters the fascial sheath. As arterial blood is aspirated, the needle is
slowly advanced until blood is no longer aspirated. The needle will now be
posterior to the artery. Half of the local anesthetic preparation is injected,
gently aspirating after every 5 cc. Then, the needle is retracted slowly until
it is anterior to the artery (when no arterial blood is aspirated). The
remainder of the local anesthetic preparation is injected at this site.
Pressure should be held over the injection site for approximately 10 minutes to
prevent hematoma formation. For short procedures, 40 cc of lido-caine 1.5% or
mepivacaine 1.5% may be used. If a longer-duration block is required, a 1:1
solution of either of the above can be mixed with bupivacaine 0.5%.